Remember the last TWO strings skipped with #@.

Remember the last TWO strings skipped with #@.
(prev_saved_doc_string*): New variables.
(Fload): Initalize prev_saved_doc_string.
(read1): Copy saved_doc_string to prev_saved_doc_string
before storing a new string in saved_doc_string.
(read_list): Look in prev_saved_doc_string as well as
in saved_doc_string.

(read1): Swap saved_doc_string_length and
prev_saved_doc_string_length.
(read_list): Negate docstring position if negative before checking
against saved_doc_string_length et al.

(read_vector): Add bytecodeflag parameter, which is
nonzero when reading a bytecode object.  If
`load-force-doc-strings' is t when reading a lazily-loaded
bytecode vector, the loaded docstring must be treated as unibyte
and passed to Fread to obtain the actual bytecode string and
constants vector.
(read1): Add extra parameter to read_vector calls.

(read1): Enable saving of doc strings on WINDOWSNT.
(read_list): Call get_doc_string instead of read_doc_string, when
forced to load doc strings.